Sucks you are going through that with them. I was extremely weary about buying one through ebay even though they were generally cheaper. I have had some bad outcomes on ebay and pretty much nothing but good outcomes on Amazon. I'm not sure how much you paid for the 60w but perhaps you could spend a few hundred more and just get the same one I did? Nearly double the power should offer more flexibility and longer tube life when being used at lower power levels is how I convinced myself I needed 100w.

100w without lightburn for $3,400: https://www.amazon.com/Engraving-Cutting-Machine-Engraver-Interface/dp/B07F3QP4FT?ref_=ast_sto_dp

If you decide to go that route, they should be able to just change your order over to the 100w and bill you the difference. Since they have somewhat inconvenienced you, they may cut some off the price to keep you happy. I would send them an email and see what they will do for you.